Using build-in joist hangars with low density blocks

[garyo]

Is it okay to sit build-in joist hangars directly on to low density 3.5N blocks, or is a course of 7N blockwork required to distribute the load?

I've checked a few manufacturers specs but they don't mention block density requirements.

http://www.parkesgroup.co.uk/index.php?page=builders_joist_buildin

e.g.

Thanks

Gary

 

[^woody^]

It's OK

 

[theoldun]

We never use timber to block joist hangers. One of the most common accidents on site.
We always build then in neatly with a 10mm joint against joist, rake joint back 10mm and heavy bead of mastic all round to stop air leakage.
If you do use them, remember you need 3 course of block or 8 course of brick laid on top before applying any load.
oldun

 

[garyo]

Mmm I think I might give them a miss then and just build the joists in!

 

[garyo]

Thread resurrection! I'm going to build my joists in and use 1cm of mastic all round, but I've read that the beams should sit directly on to the block work, rather than on to a mortar bed - is this correct? So the mastic beneath will be in a 10mm channel cut in to the thermalite?

Cheers

Gary

 

[^woody^]

You should not leave a 1cm gap around joists.

You build them in tight, and then mastic around them

They sit on the bare wall with no mortar bed - so make sure that last course is level